KR100238133B1 - Image recovery apparatus and method in video phone - Google Patents

Abstract

The present invention relates to a data transmission / reception apparatus and method for detecting an error of image data transmitted and received by a moving picture telephone and automatically recovering the error. The video telephone is provided with image input / output means for converting and outputting an image of a subject into an electrical signal and displaying the received video signal. Then, the analog video signal outputted from the video input / output means is encoded and output by an input control signal, and the encoded video signal is decoded by input of a control signal to decode the analog video signal. Image compression encoding means for outputting by means, transmission and reception entropy means for compressing and coding data output from said image compression encoding means, decoding and decompressing received data, and outputting to said image compression encoding means, and The message data and the image data output from the transmission / reception entropy means are multiplexed and output to the transmission line, the multiplexed data received from the transmission line is demultiplexed, and the image data is input to the transmission / reception entropy means. To A network interface means for extracting and outputting; and connected to the network interface means to control transmission and reception interfacing, and provide recovery request message data to the network interface means in response to an input of a recovery request signal; And a control means for outputting a recovery request response signal in response to an input of the signal, and decoding the data received by the transmission and reception entropy means to compare and check the average data length through a header code value, thereby recovering the recovery request signal when the length is determined from the average value. And received data error detection means for providing to the control means and setting the operation of the video compression encoding means to the intra mode in response to the recovery request response signal output from the control means.

Description

Image recovery apparatus and method of video telephone

1 is a block diagram of a video telephone according to the present invention.

2 is a flowchart of an image recovery request according to the present invention.

3 is an image recovery control flowchart according to the present invention.

* Explanation of symbols for main parts of the drawings

12: video input / output unit 14: R / T DPCM

16: transmission and reception entropy 18: network interface

20: reception error detection unit 22: control unit

The present invention relates to an apparatus and method for transmitting and receiving data of a video telephone, and more particularly, to an apparatus and method for transmitting and receiving data and automatically recovering an error of image data transmitted and received by a video telephone.

In general, a motion video telephone is capable of transmitting and receiving voice data and image data to and from another party using a BRD (2B + D) channel of ISDN. The basic structure of such a video telephone is disclosed in No. 22640 filed in 1992 (hereinafter referred to as "Pre-Patent Patent") filed by the present application.

The videophone disclosed in the above patent application is adapted to operate with a scheme of coding and decoding algorithms recommended in CCIT Recommendation H.261. The data of the video telephone complying with the H.261 encoding / decoding algorithm as described above is composed of a picture layer, a GOB layer, an MB layer, and a block layer. do. In this case, in the case of the image data input by QCIF, the image layer is composed of three GOBs (Group of blocks), and one GOB is composed of 33 macro blocks. One macroblock is composed of one unit block to terminate run length coding with a corresponding header. The run length coded data is transmitted after being coded with BCH (Bose Chaudhuri Hocquenghem Code), which is a channel coding scheme. In this BCH coding, one frame of framing bits and 493 bits and 18 bits of coded bits constitute one frame. The data coded by the H.261 method is coded by the channel multiplexing method recommended in CCITT Recommendation H.221 and then transmitted to the other party's video telephone through a network interface that satisfies the requirements of CCITT Recommendation I.430. .

The video telephone which transmits and receives a video by the above process transmits the image data in the initial intra mode, and thereafter, the video telephone transmits only the difference image of the previous frame and the current frame. It is supposed to transmit image data. That is, initially, one complete frame image is transmitted in the intra mode, and after that, only the changed video is extracted and transmitted in the inter mode.

As described above, in the state where the transmitting and receiving video phones transmit and receive each other's images, an unpredictable burst error or a large irregular error on a transmission network such as an ISDN transmission line error ( When a random error occurs, a phenomenon in which the received image is broken occurs. That is, the image displayed on the display screen is disturbed.

When the above phenomenon occurs, the user presses a recovery request key provided on the keypad of the video telephone to generate an image recovery request. When the recovery request signal is generated, the video telephone at the receiving end transmits a BAS (BIT Alignment Signal or Bit Rate Allocation Signal) indicating that an error has occurred in the video data. At this time, the BAS signal is transmitted to the video telephone of the other party through the transmission network. The video telephone of the other party who inputs the BAS signal switches the transmission mode so that the image data is transmitted in the intra mode in response to the reception of the signal. When the transmission mode of the video telephone on the transmission side is switched to the intra mode, a video of one complete frame is transmitted, thereby recovering the broken image on the reception side.

However, the recovery method of the conventional video telephone which recovers the data reception error by the above process, after the user sees the display screen and recognizes that the image is broken, manually recovers the image by manipulating the recovery key. I couldn't.

In addition, a problem arises that the user has to press the recovery key every time the received image is broken, causing inconvenience to the user.

Accordingly, an object of the present invention is to provide an apparatus for detecting an error state of a received video and automatically recovering an image by the signal thereof in a video communication system for transmitting and receiving a video.

Another object of the present invention is to provide an apparatus and method for detecting an error state of image data transmitted and received in a specific form and automatically transmitting the state to the counterpart.

It is another object of the present invention to provide an apparatus for detecting an error state of image data transmitted and received.

The analog video signal outputted from the video input / output means is encoded and output by an input control signal, and the encoded and received video data is decoded by input of a control signal to output an analog video signal to the video input / output means. Image compression and encoding means, transmission and reception entropy means for compressing and coding data output from the image compression encoding means, decoding and decompressing the received data and outputting the data to the image compression encoding means, and input message data. And multiplex the image data output from the transmission and reception entropy means to output to the transmission line, demultiplex the multiplexed data received from the transmission line, input image data to the transmission and reception entropy means, and extract and output message data. Is connected to the network interface means, controls transmission and reception interfacing, provides recovery request message data to the network interface means in response to the input of the recovery request signal, and responds to the input of the extracted message data. A control means for outputting a recovery request response signal, and a control request signal for the recovery request signal if a time code is exceeded by adding a threshold length that is more than an average length of all frames by checking a header code in the decoded data of the transmission and reception entropy means. And receiving data error detection means for setting the operation of the video compression encoding means to the intra mode in response to a recovery request response signal output from the control means.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a video telephone according to the present invention, which converts and outputs an image of a subject into an electrical signal and outputs the received image signal to the image input / output unit 12 and the image input / output unit 12. The video signal output from the video signal is encoded and output by the input control signal, and the encoded video data is decoded by the input of the control signal to output the analog video signal to the video input / output unit 12. Differential PCM (DPCM) 14 and the transmission and reception entropy unit 16 for compressing and coding data output from the DPCM 14 and outputting the data, and decoding and extending the received data to output the DPCM 14. ), The input control data and the data output from the transmission / reception entropy unit 16 are multiplexed and output to the transmission line, and the multiplexing is received from the transmission line. Demultiplexed data to input image data to the transmit / receive entropy unit 16, and extract and output control data to the network interface unit 18 and the network interface unit 18 to control transmit / receive interfacing. In response to the input of a fast up-date request signal (FUD-R), a BAS signal indicating a recovery request state is provided to the network interface unit 18, and is output from the network interface unit 18. The control unit 22 outputs a fast up-date request acknowledge signal (FUD-ACK) in response to the control data, and the decoding and decompression of the transmission and reception entropy unit 16 and the reception buffering time are checked. The recovery request signal FUD-R is provided to the controller 22 when the predetermined time is exceeded, and the DPCM 14 of the DPCM 14 responds to the recovery request response signal FUD-ACK output from the controller 22. Is small is composed of an intra mode, the reception data error detecting unit 20 to set a (Intra mode).

The transmission / reception entropy unit 16 of the configuration of FIG. 1 is an entropy coder 24 for run length coding the data output from the DPCM 14 and is output from the entropy coder 24. A Tx buffer 28 for buffering and outputting coded data and a BCH coder for coding and outputting data output from the Tx buffer 24 to a BCH code (hereinafter referred to as T-BCH). 32, a reception BCH decoder (hereinafter referred to as R-BCH decoder) 34 for BCH decoding and outputting the received data, and a reception buffer Rx for buffering data output from the reception BCH decoder 34. buffer) 30 and an entropy decoder 26 which run-length decodes the output of the reception buffer 30 and outputs it to the DPCM 14.

The network interface unit 18 is multiplexed with the multiplexer 36 for multiplexing and outputting data output from the transmission T-BCH coder 32 and control data output from the control unit 22. A demultiplexer 38 for outputting image data to the R-BCH 34 and outputting control data to the controller 22, a multiplexer 36 and a demultiplexer 38 And a network interface 40 connected between the transmission paths and interfacing with the network under the control of the control unit 22.

FIG. 2 is a flowchart of an image recovery request according to the present invention, which is an operation flowchart of a part of the controller 22 shown in FIG. 1, which is in the following order.

In response to the input of the recovery request signal FUD-R, the predetermined BAS data is transmitted to the counterpart through the multiplexer 18.

3 is a flowchart of an image recovery control according to the present invention, in which an operation mode of the DPCM 14 is transferred to an intra mode through the reception data error detection unit 20 in response to an image recovery request signal FUR-R signal received. Set so that the telephone on the frame is transmitted.

Before describing the operation of an embodiment according to the present invention in detail, it is assumed that video phones having the configuration as shown in FIG.

Now, when an analog video signal is output from the video signal input / output unit 12, it is input to the DPCM 14. At this time, the DPCM 14 converts the input analog image signal into a digital signal, encodes and quantizes it, and outputs the quantized image data to the entropy coder 24 as a mode corresponding to the input of the control signal. The mode signal provided to the DPCM 14 is a signal of a frame operator F0 and an inter / intra mode (IT / IR mode), which is transmitted to the received data error detector 20. Is printed from. The mode signal is provided with an initial frame operation F0 and an intra mode signal.

The DPCM 14 is operated in the intra mode by the mode operation signal as described above, and outputs one frame of image data to the mode entropy coder 24. The entropy coder 24 run-length-codes the data sequentially input to the transmission buffer 28, and the transmission buffer 28 buffers the data to the T-BCH coder 32. The T-BCH 32 transmits the runlength coded data to the multiplexer 36 by BCH coding in the manner of CCITT Recommendation H.261 as described above. The transmission buffer 32 is configured to buffer the difference between the output of the entropy coder 24 and the output of the T-BCH coder 32 during the operation of the above configuration.

The multiplexer 36 transmits data transmitted from the transmission T-BCH 32 and control data output from the control unit 22, for example, a frame alignment signal (FAS) and a bit rate, which are frame arrangement signals. A bit rate allocation signal (BAS) is multiplexed and output to the network interface 40. In the above, the FAS is a signal for synchronization of the frame, and the BAS is a bit rate allowance signal for the data protocol, and is used to receive coding information and a protocol for confirming that the audio and image coding scheme of the other party's video phone is compatible with itself. Information containing various data. The network interface 40 for inputting data output from the multiplexer 36 transmits the data to the other party through a transmission line connected to the network under the control of the controller 22.

Meanwhile, the signal output from the counterpart is received through the network interface 40, and the network interface 40 inputs the received data to the demultiplexer 38 under the control of the controller 22. The demultiplexer 38 demultiplexes the multiplexed and received data to separate and output image data and control data. The demultiplexed image data is supplied to the R-BCH 34, and the control data is supplied to the controller 22. This multiplexing operation and demultiplexing operation means that the multiplexing is performed in the form of a frame recommended in CCITT H.221 or a similar frame structure.

The R-BCH 34 which receives the data output from the demultiplexer 38 outputs the received data to the reception buffer 30 by BCH decoding the received data. As described above, the R-BCH decoder 34 BCH-decodes data of a frame transmitted and received in units of 493 bits at the transmitting side and inputs the received data to the reception buffer 30. In this case, when the transmission error is less than 2 bits per 493 bits, error correction data is compensated for by a parity bit received during BCH decoding to compensate for a frame transmission error.

As described above, the reception buffer 30 that receives the BCH decoded data outputs the received data to the entropy decoder 26. The entropy decoder 26 entropy decodes the received data and outputs the data to the DPCM 14. The entropy decoding is performed in units of one macro composed of six blocks and counts blocks at the time of decoding. The DPCM 14, which inputs the data output from the entropy decoder 26, decodes it, converts it into an analog image signal, and outputs it to the reproduction unit of the image input / output unit 12.

In the above operation state, the reception data detection unit 20 connected to the transmission / reception epitaxial unit 16 detects an error state of data reception by performing the H.261 decoding process of the transmission / reception entropy unit 16 as follows. If there is no error in the received data, the video telephones of the transmitting side and the receiving side transmit and receive video and perform video and voice communication.

If an unexpected cluster error or a large random error occurs in a transmission line or a transmission network in the above operating state, the error correction capability of the R-BCH 34 is out of range. That is, when a large number of errors occur in the received data, error detection in the R-BCH 34 becomes impossible. Therefore, when error correction of the received data becomes impossible, the cluster error spreads to the data received later. When such a clustering error occurs, a phenomenon in which the reproduced screen is broken (flooded) occurs. The error data spread by the R-BCH decoder 34 is input to the entropy decoder 26 through the reception buffer 30. At this time, the entropy decoder 26 executes run length decoding in units of 1 macro. As described above, the one macro includes six block data, and the entropy decoder 26 increments a counter for counting the number of blocks for each run length decoding of one block data. At this time, since each block data is spread by cluster error, the number of data bits of each block is increased. As a result, a counter value counting data blocks in one macro block is 6 or more block values due to block collapse. Will have Accordingly, as the burst error occurs due to an error such as a transmission path in the received data, the interval of the MBA increases as the number of blocks of the received data increases. As described above, when the interval of the MBA is increased, the interval of GBSC, which is a start position of a group of blocks (GOBs) maintaining a constant interval, is increased. In addition, when the spreading of the data packet length occurs as described above, the interval of the position PSC of the picture start point of the image data indicating the start of the image is increased in series.

At this time, the received data error detection unit 20 connected to the entropy decoder 26 corrects the error of the previous frame and the current frame by checking the MBA interval, the GBSC interval or the PSC interval. If the interval of the frame changes abruptly due to the characteristics, the error state of the received data is determined. When the reception data error detection unit 20 which performs the above operation determines the error state of the reception data, the reception data error detection unit 20 outputs the recovery request signal FUD-R to the control unit 22. In this case, the control unit 22 scans the input port at predetermined intervals in step 250 to search for the input of the recovery request signal FUD-R in step 52.

Accordingly, when the reception data error detection unit 20 outputs a recovery request signal FUD-R indicating a recovery state of the screen while the control unit 22 performs steps 50 and 52 of FIG. ) Detects its state in step 52. In step 52, the controller 22 determines that the recovery request signal FUD-R is input, and outputs the BAS code scheduled to the multiplexer 36 in step 54. The above-mentioned BAS code is binary data of " 0101 0001 ", which is data of a protocol for requesting transmission of image data in intra mode (recovery of a screen). The multiplexer 36, which receives the BAS data of 0101 0001 output from the controller 22, multiplexes the input data according to the recommendation of CCITT H.221 and transmits it through the network interface 40. Therefore, the recovery request signal BAS output from the control unit 22 on the receiving side is transmitted to the transmitting side transmitting the image data in the H.221 method.

As described above, the BAS data transmitted from the receiving side is input to the demultiplexer 38 through the network interface 40 in the transmitting side video telephone, and the video telephone of the other side is operated as follows.

The demultiplexer 38 in the video telephone on the transmitting side demultiplexes a signal input through the network interface 40 to separately output image data and BAS control data. The separated image data is input to the R-BCH decoder 34, and the BAS data is input to the control unit 22. The controller 22 which inputs the data output from the demultiplexer 38 determines that the data has been received in step 356 and searches whether the received data is a predetermined BAS coordination. That is, it is searched whether the received BAS code is "0101 0001". If the BAS code received as a result of the search is “0101 001”, the controller 22 determines that the recovery request signal FUD-R has been transmitted from the video phone of the other party, and in step 60 the recovery request response signal FUD-ACK. Is output to the reception error detection unit 20. That is, the controller 22 sets the transmission mode of the image data from the inter mode (macro block transmission) to the intra mode in step 60 so that the video signal in units of frames is transmitted. On the other hand, the reception error detection unit 20 that receives the recovery request response signal FUD-ACK supplies an intra mode signal (IT mode) to the DPCM 14 in response to the input of the signal. The DPCM 14 outputs the image data of the intra mode, that is, 99 macro blocks of up to one frame, to the entropy coder 24 by the signal output from the reception error detector 20. When the DPCM 14 outputs the image data in the intra mode as described above, the receiving side receives the correct image.

In the above-described embodiment of the present invention, an error state of received data is detected at intervals of MBA or GBSC. However, those skilled in the art may use the above characteristics to determine the data of the specific reception buffer 30. It should be noted that data can be detected as a quantity. For example, it is detected that the amount of data in the reception buffer 30 that buffers data from the R-BCH decoder 34 to the entropy decoder 26 increases rapidly in accordance with the decoding operation by the error data of the entropy decoder 26. It should be noted that the data reception error state may be determined, which does not depart from the scope of the present invention.

As described above, the present invention automatically detects an error in data due to a clustering error occurring on a network in a state of transmitting and receiving moving image data, and automatically transmits a screen recovery request signal to a video telephone of the other party, and requests an image recovery request. By automatically setting the transmission of the image data to the intra mode by the input of the signal, the video communication of the moving image telephone can be made smoother, and there is an advantage that the user can be convenient.

Claims (8)

An image recovery apparatus of a video telephone having an image input / output means for converting and outputting an image of an object into an electrical signal and displaying the received image signal, wherein an image signal of an analog output from the image input / output means is input. Image compression encoding means for encoding and outputting the video signal encoded by the control signal, decoding the received image data by the input of the control signal, and outputting the analog video signal to the video input / output means, and outputting from the video compression encoding means. Compression, coding, and outputting the received data, transmission and reception entropy means for decoding and decompressing the received data and outputting the data to the video compression encoding means, and multiplexing the input message data and the image data output from the transmission and reception entropy means. Output to, and send Network interface means for demultiplexing the multiplexed data received from the network, inputting image data to the transmission and reception entropy means, and extracting and outputting message data; and controlling the transmission and reception interface connected to the network interface means and restoring a recovery request signal. Control means for providing the recovery request message data to the network interface means in response to an input of a; and outputting a recovery request response signal in response to the input of the extracted message data; The video compression encoding means is provided in response to the recovery request response signal outputted from the control means when the code is checked to provide a recovery request signal to the control means when a time exceeding a threshold length that is expected than the average length of all frames is exceeded. Intra action Video image restoration apparatus of the telephone characterized in that it consists of a reception data error detecting means to set the draw. The transmission and reception means of claim 1, wherein the transmission and reception entropy means comprises: transmission coding means for run length coding the data output from the video compression encoding means and BCH coding and outputting the frame having a transmission form; And transmission data decoding means for performing BCH decoding on the data, and performing run length decoding on the BCH decoded data and outputting the data to the video compression encoding means. The transmission coding means according to claim 2, wherein the transmission coding means comprises: an entropy coding means for run length coding the data output from the video compression coding means, and a buffered output of the coded data output from the entropy coding means. Means, and transmission BCH coding means for coding and outputting data output from the transmission buffering means into a BCH code. 4. The apparatus of claim 3, wherein the transmission data decoding means comprises: reception BCH decoding means for BCH decoding and outputting received data, reception buffering means for buffering data output from the reception BCH decoding means, and the reception buffering means. And entropy decoding means for run-length decoding the output of the output to the video compression encoding means. The received data error detecting means detects an error of the received data by comparing the interval of the MBA at run length decoding with the BCH decoded data with the interval of the MBA determined through an average value to detect a recovery request signal. And an image recovery apparatus for outputting the video telephone. The received data error detecting means compares the interval of GBSC due to the increase of the interval of MBA at run length decoding with the received data by comparing the interval of GBSC with a preset interval of GBSC. And a recovery request signal is outputted to said control means. The receiving data error detecting means detects an abrupt amount of data in the receiving buffering means for buffering the output data of the receiving BCH decoding means with an entropy decoding means to detect an error in the received data. And detecting and supplying a recovery request signal to said control means to said control means. An image input / output means, an image compression encoding means, a transmission / reception entropy means, a network interface means, a control means, and detecting an error of the received data and supplying it to the control means and in response to input of a recovery request response signal. An image recovery method of a video telephone of a video telephone having a received data error detecting means for controlling the operation of the compression encoding means in an intra mode, and transmitting and receiving a video signal with a counterpart, comprising: a recovery request signal in response to error detection of the received data; Transmission of error detection information for multiplexing the transmission data to the other party and transmitting the data of the frame image by setting the data transmission mode to the intra mode in response to the input of the recovery request signal transmitted from the other party. Method characterized by done.